A mutex is a common type of lock used to serialize concurrent access by multiple
threads to shared resources. While support for POSIX mutexes in the QNX Neutrino
Realtime OS dates back to the early days of the system, this area of the code
has seen considerable changes in the last couple of years.

Yes the desktop OS along with the dev SDK is available for download at the qnx website. However payed support costs an arm an a leg (or at least last time i tried it) so you are going to depend on written documentation and community for help unless you want to pay.